The metaphorical hymen of the anus. Like the hymen, this is "broken" upon penetration to the aformentioned area, eliminating the subject's anal virginity.
So...is that behymen still intact?
An imaginary version of a woman's hymen that is inside the anus of every gay man. It is "broken" the first time he is anally penetrated.
I heard Lance Bass broke his beymen last week. Guess who broke it. Joey Fatone.